1. Field of the Invention
The invention is generally related to the field of manufacturing compositions comprising an acid gas and a matrix gas having reduced moisture, and which are stable in acid gas concentration for more than an insignificant time period. The invention is also related to articles of manufacture containing these compositions, such as metal cylinders containing the compositions, ton units containing the compositions, and the like.
2. Related Art
Moisture is known to react with reactive gases, such as the so-called “acid gases”, for example, hydrogen sulfide, carbonylsulfide, carbondisulfide and mercaptans (mercaptans are also referred to as thiols) to form a complex compound. (The term “acid gas” is used herein to denote either gas phase, liquid phase, or mixture of gas and liquid phases, unless the phase is specifically mentioned.)
One problem presents itself: if one is interested in producing reactive gas standard compositions, in other words reactive gases having a known concentration of one of these gases in a matrix or carrier fluid, then one must consider how to reduce or remove the moisture. Gas standards may have to have, and preferably do have, a long shelf life, since the standard reactive gas may not be required immediately after production. A source of reactive gas may contain a considerable amount of moisture. Therefore, the reduction or removal of moisture from the reactive gas is of primary importance if the stability of the reactive gas in the standard gas is to be maintained. It has also recently been observed that moisture in the matrix gas (prior to its being mixed with the acid gas) contributes to the problem, for if one removes moisture from the reactive gas, and then mixes the dried reactive gas with a wet matrix gas, the problem has not been entirely solved, even if the moisture level in the matrix gas is comparatively low.
A second, related problem involves the containers that the reactive gas standards are stored in. If metal or metal lined, reactive gases will react with and/or become adsorbed onto the metal, and will ultimately change the concentration of the reactive gas.
Grossman et al. (U.S. Pat. No. 4,082,834) describes alloys, such as alloys of nickel, titanium, and zirconium, that react with water and reactive gases (such as hydrogen, hydrogen-containing compounds such as hydrocarbons, carbon monoxide, carbon dioxide, oxygen, and nitrogen) at temperatures ranging from about 200° C. to about 650° C. While the patent does not discuss acid gases, it is apparent that hydrogen sulfide, carbonyl sulfide, and mercaptans are hydrogen-containing compounds, so that there would not be any expected benefits using these alloys to remove moisture from these acid gases. While carbondisulfide does not contain hydrogen, and therefore there could be some moisture reduction from a composition comprising carbondisulfide and moisture using these alloys, the high temperature is prohibitive for commercial use.
Tamhankar et al. (U.S. Pat. No. 4,713,224) describes a one-step process for removing minute quantities of impurities from inert gases, where the impurities are selected from the group consisting of carbon monoxide, carbon dioxide, oxygen, hydrogen, water and mixture thereof. The process comprises contacting the gas with a particulate material comprised of nickel in an amount of at least about 5% by weight as elemental nickel and having a large surface area, from about 100 to about 200 m2/g. There is no disclosure of removal of moisture from reactive gases; there is therefore no discussion or suggestion of moisture removal from reactive gases, moisture removal from matrix gases and mixing same to form a standard gas composition.
Tom et al (U.S. Pat. Nos. 4,853,148 and 4,925,646) discloses processes and compositions for drying of gaseous hydrogen halides of the formula HX, where X is selected from the group consisting of bromine, chlorine, fluorine, and iodine. The patent describes the use of, for example, an organometallic compound such as an alkylmagnesium compound, on a support. The halide is substituted for the alkyl functional group. Suitable supports are, alumina, silica, and aluminosilicates (natural or synthetic). However, there is no description or suggestion of reducing or removing moisture from sulfur-containing reactive gases, or of removal of moisture from matrix gases and mixing the reduced moisture gases to form a standard gas. Alvarez, Jr. et al. (U.S. Pat. No. 5,910,292) describes a process and apparatus for removal of water from corrosive halogen gases, using a high silica zeolite, preferably high silica mordenite. The patent describes removing moisture down to less than or equal to 100 ppb water concentration in halogen gases, particularly chlorine- or bromine-containing gases, but once again, there is lacking any teaching of suggestion of standard gas compositions. U.S. Pat. No. 6,183,539 discloses utilizing high sodium, low silica faujasite particles for the adsorption of carbon dioxide and water vapor from gas streams. The disclosed types of gas streams in which this type of high sodium, low silica faujasite crystals can be utilized includes air, nitrogen, hydrogen, natural gas, individual hydrocarbons and monomers, such as ethylene, propylene, 1,3 butadiene, isoprene and other such gas systems. There is no mention of sulfur-containing acid gas purification using the faujasites, or production of standard gas compositions.
U.S. Pat. No. 4,358,627 discloses use of “acid resistant” molecular sieves, such as that known under the trade designation “AW300”, for reducing the chloride concentration in chlorinated liquid hydrocarbons that contain an ethylenically unsaturated chlorinated hydrocarbon, water and hydrogen chloride. The method includes providing certain nitrogen-containing compounds in the system and contacting the system with the molecular sieve. There is no disclosure or suggestion, however, of removal or reduction of moisture from gas phase compositions, or production of standard gas compositions.
Given the problems of moisture reacting with sulfur-containing acid gases and other reactive gases, and the fact that some or all reactive gases will react with metals, there is a definite and unmet need for standard gas compositions, articles of manufacture including those standards which are stable over reasonable periods of time, and methods of producing same.